In vitro serial subculture to improve rooting of Eucalyptus urophylla

Abstract

The aim of this study was to improve the rooting efficiency of Eucalyptus urophylla clones by in vitro reinvigoration/rejuvenation in two clones (02 and 04) from the breeding program of the V&M Florestal company. An in vitro culture began with 200 meristems of each clone, which were excised, disinfected, and inoculated in culture medium. When shoots from these first meristems inoculated reached a height of 3 cm, 100 new meristematic regions of 0.5 cm were isolated and inoculated in culture medium. The other shoots from were inoculated in a rooting medium, where they remained for 30 days. After this period, the plants were acclimatized and used as stock plants for shoot production in a commercial nursery. This process was repeated until the shoots attained an ex vitro rooting rate of more than 80%. After reinvigoration/rejuvenation of clones 02 and 04, the relationship between rooting and the presence of starch and phenolic compounds at the base of the minicuttings was histochemically analyzed. For clone 02, three in vitro subcultures were needed to increase the rooting rate, and for clone 04, only one in vitro subculture was required. In vitro reinvigoration/rejuvenation is a determining factor for greater rooting efficiency of minicuttings of 02 and 04 clones. Production of sclerenchyma fibers around the root vascular cylinder and starch and phenolic compound production are directly related to rooting efficiency.